This invention relates generally to methods and chemicals for extending the shelf life of corn tortillas or wheat tortillas, and specifically to the preservation of corn tortillas or wheat tortillas by use of a mixture containing propionic acid, phosphoric acid, and benzoic acid.
Tortillas are flat breads produced by baking doughs prepared with corn flour or wheat flour. Dough prepared from corn flour is sometimes called xe2x80x9cmasa.xe2x80x9d Masa is typically prepared from a nixtamalized corn masa flour, cooked corn, corn flour, or a mixture of these. Tortillas are a food staple in Mexico and Central America and are growing in popularity in the United States. Tortillas are currently available to consumers through retail outlets such as supermarkets and grocery stores. The term xe2x80x9ctortilla,xe2x80x9d to at least for the purposes of this application, includes such similar foods made from corn- or wheat-based dough, such as tamale shels, soft and hard taco shells, tortilla chips, tostados, burrito shells, pita bread, pocket bread, Jewish bread, corn bread, pizza crusts, and similar foods made from corn- or wheat-based dough. The term xe2x80x9ctortilla flourxe2x80x9d encompasses corn flour, wheat flour, corn masa flour, and cooked corn.
A problem with the retail production of tortillas is that the tortillas have a limited shelf life without the use of antimicrobial preservatives. Various antimicrobial preservatives have been proposed, however they have the limitations of increasing the cost of producing tortillas and/or adversely affecting the taste and odor. Naturally, extending tortilla shelf life without prohibitively increasing the tortilla production costs, or detrimentally affecting the taste or odor of the tortillas, results in better tortilla preservation.
The primary indications of spoilage for tortillas are an off odor or taste and the formation of mold. Another mechanism for spoilage is the staling of a tortilla with the passage of time. The present invention is not directed to staling, which typically occurs through the crystallizing of starch. The shelf life of a tortilla for the purposes of this application can be said to last from the time the tortilla is made until mode is visible, or a fermented or spoiled odor can be detected, whichever occurs first. The primary causes of spoilage are bacteria, mold, and yeast. In the laboratory, shelf life of varying formulations of tortillas can be compared by monitoring the output of carbon dioxide produced by the bacteria, mold, and yeast.
Preservatives and antimicrobial agents for use in tortillas shown in the prior art include: low molecular weight fatty acids such as acetic, propionic, and butyric acids (U.S. Pat. No. 3,859,499), or potassium sorbate (Pelaez and Karel, 4 xe2x80x9cDevelopment and Stability of Intermediate Moisture Tortillas,xe2x80x9d 4 Journal of Food Processing and Preservation 51-65 (1980)); sorbic acid (U.S. Pat. No. 3,853,997); esters of para-hydroxybenzoic acid or parabens (U.S. Pat. No. 3,853,997); glycerol, corn solids, and salt to lower the water activity (Pelaez and Karel, supra); and dimethyl fumarate (Islam et al, xe2x80x9cMold Inhibition in Tortilla by Dimethyl Fumarate,xe2x80x9d 8 Journal of Food Processing and Preservation 41-45 (1984)).
Tortilla producers and masa flour manufacturers commonly treat their tortilla flour with dry blends of sodium or calcium propionate for mold control, and potassium sorbate for bacteria and yeast control. Because these preservatives generally perform better with increasing acidity, acidulants, such as fumaric acid or citric acid, are used to reduce pH levels. A major drawback resulting from this type of preservative mixture is the lingering after-taste of the acidulant. These preservative mixtures have successfully increased the shelf life of tortillas in most cases. However, the taste of tortillas containing these preservatives has not been satisfactory. Also, the supply of some of these preservatives has been limited, making them difficult or expensive to obtain.
Due to the dissociation of acids at higher pH levels, weak acids do not perform well as preservatives at high pH levels. For this reason, it is often necessary to add acidulants to basic foods in order to utilize the antimicrobial action of weak acids. Phosphoric acid is well-known as an acidulant, and is routinely used to reduce the pH levels in foods so that weak lipophilic acids may be added as preservatives. However, the amount of phosphoric acid that must be used to reduce the pH level of tortillas to an acceptable level has been sufficient to impart a noticeable unpleasant taste characteristic to the tortillas.
Wheat flour tortillas have traditionally been preserved with a dry preservative mixture consisting of calcium propionate as a mold and rope inhibitor, an acidifier such as fumaric or citric acid, and usually potassium sorbate or sorbic acid for control of yeast and bacteria. This mixture has been effective in extending the shelf life of wheat flour tortillas; however, recently the cost of such mixtures has inflated due to shortages of potassium sorbate and sorbic acid. Furthermore, this mixture has unfavorable taste characteristics. For example, fumaric acid has a lingering aftertaste as a result of its low solubility in water, which allows it to sit on the tastebuds and slowly dissolve. Citric acid gives a sharp burst of sourness at the initial taste, which is also undesirable. Mixing the dry ingredients of this prior art mixture is labor intensive and prone to variability because the powders must first dissolve and then disperse in the dough during mixing.
Propionic acid and calcium propionate are widely used to prevent the growth of mold in bakery products. Both are especially well-suited for use in leavened bakery goods as having minimal effect on yeast. Propionic acid and calcium propionate are preferred preservatives because they have little affect on the odor or taste of the finished product. As a salt of a weak acid, calcium propionate is most effective in the lower pH range, and typically is used with an acidulant. Weak organic acids that serve as preservatives have an ideal pH range, which is directly connected to the pKa, or dissociation constant of the acid, when fifty percent (50%) of the total acid is undissociated or free to act as a preservative. Since the pKa of most organic acids lies between pH 3 and 5, acidifiers are typically used to decrease the pH of food in order to increase the undissociation, or xe2x80x9cactivatexe2x80x9d the preservative. John R. Chipley, xe2x80x9cSodium Benzoate and Benzoic Acid,xe2x80x9d in Antimicrobials in Foods 12-13 (P. Michael Davidson and Alfred L. Branen eds., 2d ed. 1993). For example, the pKas of propionic acid and benzoic acid are 4.87 and 4.19, respectively. At these pH levels, fifty percent (50%) of the acid is undissociated. If the pH of a food is 5.4, only twenty percent (20%) of the propionic acid and a mere 7.75% of the benzoic acid would be undissociated and available as a preservative. The optimum anitmicrobial pH range for benzoic acid is 2.5 to 4. George J. Banwart, Basic Food Microbiology 602.
Some tortilla manufacturers add a liquid preservative to the tortilla during processing. Typical liquid formulations use propionic acid for mold control and phosphoric acid as an acidulant. Because these mixtures include a single preservative, rather than a combination of preservatives, high doses are required to achieve the desired shelf life. Despite the high levels of preservative, these liquid formulations are often not effective in controlling fermentation during high-stress seasons. A major negative taste resulting from this type of liquid formulation is that of phosphoric acid.
Benzoic acid is a well-known food preservative. It is generally used only in very acidic foods such as pickles, soft drinks and dressings. See N. J. Russell and G. W. Gould, Food Preservatives 19 (1991). Its use is typically limited to foods having a pH below 4.5. John R. Chipley, xe2x80x9cSodium Benzoate and Benzoic Acid,xe2x80x9d in Antimicrobials in Foods 11, 27 (P. Michael Davidson and Alfred L. Branen eds., 2d ed. 1993). Benzoic acid is also known to impart an off flavor. Id. Because of the narrow pH range in which it has generally been effective and because of its off-flavor, it is being replaced by other preservatives. (Chipley, supra, at 27). Benzoic acid has not been effective to control the growth of high-levels of microorganisms. Id. Because tortillas generally have a pH level above the optimum effective antimicrobial range of benzoic acid, benzoic acid has not been commonly used as a tortilla preservative.
Retail markets are emerging for uncooked tortilla dough and uncooked tortillas, allowing consumers to make fresh tortillas themselves. The dough is similarly susceptible to spoiling by the action of yeast, bacteria, and mold. The shelf life of dough or uncooked tortillas lasts from the time at which the dough is made until the time at which mold is visible, or the time at which a fermented or spoiled odor can be detected, whichever occurs first. A shelf life of less than twenty-four hours is expected for the unrefrigerated, unpreserved corn-based dough. A preservative which effectively retards or prevents the growth of various microorganisms including mold, bacteria and yeast, in order to extend the shelf life of tortillas and tortilla dough. without imparting a negative taste, or prohibitively increasing the cost is particularly desirable. Therefore, a continuing need exists to provide such preservation.
The present invention substantially eliminates the difficulties encountered in the prior art discussed above.
Accordingly, it is an object of the present invention to provide an improved preservative for extending the shelf life of tortillas made from corn flour or wheat flour which eliminates or retards the growth of yeast, mold and bacteria without adversely affecting the taste of the tortillas.
It is an object of the present invention to provide good tasting, affordable tortillas with an extended shelf life made from corn flour or wheat flour.
It is an object of the present invention to provide corn flour or wheat flour that has been treated with a preservative such that tortillas, and similar foods, produced from the flour will have an extended shelf life without having adverse taste characteristics or prohibitive costs.
It is an object of the present invention to provide a corn-based or a wheat-based dough or raw tortilla that has an extended shelf life without having adverse taste characteristics or prohibitive cost.
It is an object of the present invention to provide a corn-based or a wheat-based dough suitable for baking into tortillas or similar products, such that the tortillas or similar products made from the dough have an extended shelf life without having adverse taste characteristics or prohibitive cost.
It is an object of the present invention to provide a liquid preservative composition that can be used to extend the shelf life of tortillas made from corn flour or wheat flour.
These and other objects will become apparent upon reference to the following specification and claims.
By the present invention, it is proposed to meet these objectives and other more specific objectives which will become apparent as the description proceeds. To this end, a preservative process is provided for extending the shelf life of tortillas, tortilla dough, and similar foodstuffs made from corn flour or wheat flour. The preservative comprises benzoic acid, propionic acid, and phosphoric acid, with the ratio of propionic acid to phosphoric acid by weight being at least 2.5 to 1.